Imprint lithography utilizing room temperature embossing

Details Imprint lithography utilizing room temperature embossing Imprint lithography utilizing room temperature embossing

2001-10-01

2004-11-09

Vargot, Mathieu D. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Optical article shaping or treating

Light polarizing article or holographic article

C264S320000

Reexamination Certificate

active

06814898

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to methods and devices for forming submicron sized features and patterns in large area substrate surfaces by means of imprint lithography. The invention has particular utility in the formation of servo patterns in the surfaces of substrates utilized in the manufacture of data/information storage and retrieval media, e.g., hard disk magnetic media.
BACKGROUND OF THE INVENTION
Optical-based lithographic techniques are widely employed in the fabrication of integrated circuits (ICs) and other devices requiring very fine-dimensioned patterns or features. However, the constantly increasing demands of micro-miniaturization for increased data storage and computation require fabrication of devices with ever smaller dimensions, which demands tax or even exceed the limits of conventional optical lithographic patterning processes utilizing visible light. As a consequence, intense research has been conducted on ultra-violet (UV), X-ray, electron beam (e-beam), and scanning probe (SP) lithography. However, while each of these techniques is capable of providing high resolution, finely-dimensioned patterns and features, the economics of their use is less favorable, due to such factors as limitations arising from wavelength-dependent phenomena, slow e-beam and SP writing speeds, and difficulties in the development of suitable resist materials.
Thermal imprint lithography has been recently studied and developed as a low cost alternative technique for fine dimension pattern/feature formation in the surface of a substrate or workpiece, as for example, described in U.S. Pat. Nos. 4,731,155; 5,772,905; 5,817,242; 6,117,344; 6,165,911; 6,168,845 B1; 6,190,929 B1; and 6,228,294 B1, the disclosures of which are incorporated herein by reference. A typical thermal imprint lithographic process for forming nano-dimensioned patterns/features in a substrate surface is illustrated with reference to the schematic, cross-sectional views of FIGS.
1
(A)-
1
(D).
Referring to FIG.
1
(A), shown therein is a mold
10
(also known as a stamper or imprinter) including a main or support body
12
having upper and lower opposed surfaces, with a molding layer
14
(also referred to as an imprinting surface) formed on the lower opposed surface. As illustrated, molding layer
14
includes a plurality of features
16
having a desired shape or surface contour. A substrate or workpiece
18
carrying a thin film layer
20
on an upper surface thereof is positioned below, and in facing relation to the molding layer
14
. Thin film layer
20
, e.g., of polymethyl methacrylate (PMMA), may be formed on the substrate/workpiece surface by any appropriate technique, e.g., spin casting.
Adverting to FIG.
1
(B), shown therein is a compressive molding step, wherein mold
10
is pressed into the thin film layer
20
in the direction shown by arrow
22
, so as to form depressed, i.e., compressed, regions
24
. In the illustrated embodiment, features
16
of the molding layer
14
are not pressed all of the way into the thin film layer
20
and thus do not contact the surface of the underlying substrate
18
. However, the top surface portions
24
a
of thin film
20
may contact depressed surface portions
16
a
of molding layer
14
. As a consequence, the top surface portions
24
a
substantially conform to the shape of the depressed surface portions
16
a
, for example, flat. When contact between the depressed surface portions
16
a
of molding layer
14
and thin film layer
20
occurs, further movement of the molding layer
14
into the thin film layer
20
stops, due to the sudden increase in contact area, leading to a decrease in compressive pressure when the compressive force is constant.
FIG.
1
(C) shows the cross-sectional surface contour of the thin film layer
20
following removal of mold
10
. The molded, or imprinted, thin film layer
20
includes a plurality of recesses formed at compressed regions
24
which generally conform to the shape or surface contour of features
16
of the molding layer
14
. Referring to FIG.
1
(D), in a next step, the surface-molded workpiece is subjected to processing to remove the compressed portions
24
of thin film
20
to selectively expose portions
28
of the underlying substrate
18
separated by raised features
26
. Selective removal of the compressed portions
24
may be accomplished by any appropriate process, e.g., reactive ion etching (RIE), wet chemical etching, or ion or electron beam irradiation. The thus-patterned thin film layer
20
may subsequently be utilized as an etch mask or irradiation mask for selective removal of the exposed substrate portions
28
, after which the patterned thin film layer
20
is itself selectively removed, leaving a patterned substrate
18
.
The above-described imprint lithographic processing is capable of providing sub-micron-dimensioned features, as by utilizing a mold
10
provided with patterned features
16
comprising pillars, holes, trenches, etc., by means of e-beam lithography, RIE, or other appropriate patterning method. Typical depths of features
16
range from about 5 to about 500 nm, depending upon the desired lateral dimension. The material of the molding layer
14
is typically selected to be hard relative to the thin film layer
20
, the latter typically comprising a thermoplastic material which is softened when heated. Thus, suitable materials for use as the molding layer
14
include metals, dielectrics, semiconductors, ceramics, and composite materials. Suitable materials for use as thin film layer
20
include thermoplastic polymers which can be heated to above their glass temperature, T
g
, such that the material exhibits low viscosity and enhanced flow.
While nanoimprint lithographic techniques, such as described above, afford the possibility of a low-cost, mass manufacturing technology for fabrication of sub-100 nm structures, features, etc., for semiconductor ICs, integrated optical, magnetic, and mechanical devices, the problem of non-uniform replication and sticking of the thermoplastic polymer materials to the molding layer
14
when the latter is applied to a large-area substrate, e.g., as in the formation of servo patterns in 95 mm diameter disks used in hard disk drives, arising from differences in thermal expansion/contraction characteristics of the mold and substrate materials, has not heretofore been addressed.
For example, according to conventional practices in thermal imprint lithography, it is normal for the components of the imprinting system, i.e., substrate, resist layer, and mold or imprint tool (referred to in the art as a stamper/imprinter) to undergo large thermal swings or cycling, e.g., within a range of about 100° C. The 100° C. increase in temperature experienced by the thin film resist layer, typically of a thermoplastic polymer, causes the viscosity to decrease and hence increase the fluid flow characteristics thereof, which in turn, allows accurate replication of the features of the stamper/imprinter surface. However, a significant problem associated with this technique when utilized in certain applications is the dissimilar thermal expansion/contraction characteristics of the molding and thin film resist layers due to their entirely different materials properties, which dissimilarity results in degradation of imprint quality, as by deformation of and/or damage to the replicated thin film resist layer after the imprinting process is completed, as further explained below.
Imprint lithography tools, variously termed molds, stampers, imprinters, masks, etc., conventionally have been fabricated by electroforming nickel (Ni) or copper (Cu) onto a master plate comprising a patterned photoresist, or by etching through a substrate, e.g., of silicon (Si), coated with a layer of patterned photoresist. The former technique is typically utilized in the replication of vinyl audio records and optical disks; whereas the latter technique has been utilized to fabricate tools having very small feature sizes, e.g., ~20 nm, by means of e-beam techniques. Howev

Affiliated with

Also associated with

Rating

Imprint lithography utilizing room temperature embossing does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Imprint lithography utilizing room temperature embossing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Imprint lithography utilizing room temperature embossing will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3312189